A self-consistent estimate of O<sup>+</sup> + N<sub>2</sub> − rate coefficient and total EUV solar flux with λ < 1050 Å using EISCAT observations

Abstract

Abstract. There are di erences between existing models of solar EUV with k < 1050 A Ê and between laboratory measurements of the O + + N 2 ± reaction rate coecient, both parameters being crucial for the F2-region modeling. Therefore, indirect aeronomic estimates of these parameters may be useful for qualifying the existing EUV models and the laboratory measured O + + N 2 ± rate coe cient. A modi®ed self-consistent method for daytime F2-region modeling developed by Mikhailov and Schlegel was applied to EISCAT observations (32 quiet summer and equinoctial days) to estimate the set of main aeronomic parameters. Three laboratory measured temperature dependencies for the O + + N 2 ± rate coe cient were used in our calculations to ®nd self-consistent factors both for this rate coe cient and for the solar EUV¯ux model from Nusinov. Independent of the rate coe cient used, the calculated values group around the temperature dependence recently measured by Hierl et al. in the 850±1400 K temperature range. Therefore, this rate coe cient may be considered as the most preferable and is recommended for aeronomic calculations. The calculated EUV¯ux shows a somewhat steeper dependence on solar activity than both, the Nusinov and the EUVAC models predict. In practice both EUV models may be recommended for the F2-region electron density calculations with the total EUV¯ux shifted by 25% for the EUVAC and Nusinov models, correspondingly.